1. Field of the Invention
The present invention relates to a non-metallic joint prosthesis of the type primarily intended for use in replacing damaged joints between long bones of the human body. Also disclosed and claimed are the method for fabricating the prosthesis and a method for repairing damaged joints using the prosthesis.
2. Description of the Prior Art
During the past decade the ability to treat patients with joint problems has become more evident. Due primarily to the pioneer work of Charnly in England, one of the major weightbearing joints in the body, the hip joint, has become easily replaceable with artificial components. In similar fashion, small joints in the hands, requiring delicate and fine motor control, have also become amenable to replacement. The patients most commonly requiring this type of treatment are patients with rheumatoid arthritis and other forms of arthritis. Traumatic disruption of the joints plays a minor part where the placement of a joint prosthesis is called for. It is estimated that over 25,000 such joint substitutes have been placed each year.
Under state-of-the-art techniques, silicone rubber joints are most commonly utilized. There are different variants of these joints, but in principle they are all quite similar. While the silicone rubber joints are clearly acceptable, there are two factors that preclude their being the ideal, or optimal, joint prosthesis.
The first major difficulty is identified as implant fracture which simply results from "wear and tear." The silicone rubber cannot withstand the repeated motion experienced in joints, so it fractures. This results in a major complication requiring a substitution of the joint and unwarranted replacement of parts, with major hospitalization, anesthetic and other ancillary expenses. The second major problem is related to the inability of the silicone to be incorporated in the hard or soft tissue that surrounds the silicon rubber prosthesis. Therefore, with continuous joint movement, the ends of the prosthesis become loose, and there is widening and destruction of the bone with which the prosthesis is in contact.
Another type of joint prosthesis currently available is known as the Mayo clinic implant. The Mayo clinic implant comprises a metal ball and socket structure. As with the silicon rubber prosthesis, this implant also exhibits certain undesirable characteristics. Of particular importance is the inapplicability of a Mayo clinic implant as for replacing finger joints. The implant does not provide sufficient lateral stability for such joints, and will not stay in place under skin such as that surrounding finger joints.
It is therefore apparent there is a great need in the art for a joint prosthesis suitable for use in the human body and decreasing, if not eliminating, the undesirable and deleterious effects associated with state-of-the-art prosthetic joints. Of course, such a joint prosthesis must be fabricated from a material suitable for implanting within the human body. With particular regard to the rising cost of medical treatment and care throughout the world, it is furthermore desirable that the joint prosthesis be relatively easy to manufacture and to implant. For similar reasons, as well as for the well-being of the patient, such a joint prosthesis should have an anticipated lifetime coincident to that of the patient.